Cutting fluids are commonly applied during machining to disperse heat from the cutting tool and workpiece. High cutting temperatures decrease tool life, reduce cutting speeds, and reduce the quality of surface finishes. This is a direct result of tool wear, which tests have shown increases exponentially with temperature.
Cutting fluids also lubricate the tool during cutting. The lubrication increases tool life as it allows material to be sheared with less friction. Lubrication can also prevent welding, which can lead to tool or part failure.
Additionally, cutting fluid applied with pressure will remove chips from the cutting zone that can cause friction and reduce cutter life.
Presently, cutting fluids are applied with a pressure pump. Pumping cutting fluid to the cutting zone is usually accomplished with hoses and nozzles. However, this method of spraying has the following drawbacks:
1) it is somewhat unsafe since the operator must stop machine motion and adjust the hoses and flow while the spindle is turning;
2) it causes delays during machining but before and after each tool change while the operator adjusts the hoses for each cutter and moves the hoses away from the tool changer arm;
3) it can be ineffective in many cutting configurations, like slotting, where the coolant is unable to reach the cutter end buried in the material.
However, more modern machines allow cutting fluid to be pumped through the machine spindle and tool adapter. Special tools with through bores are used that enable the fluid to reach the cutting zone. The "through-the-spindle" method has advantages over the hose and nozzle method, such as: good penetration of fluid, high pressure capability that removes chips from the cutting zone, and no hoses to adjust. However, this method requires costly tools that are often difficult to locate; and it cannot be used with small diameter tools. As a result, this type of arrangement can only be used with a limited number of tools.